This afternoon I pulled the thermostat, which I will replace. The thermostat sits inside a housing with an integrated a water outlet. When the engine reaches operating temperature, the thermostat opens and allows water and coolant to flow through the outlet and out to the radiator, to cool the engine.
The housing is bolted into three studs on the front of the head. I used a 1/2″ socket in my wrench to remove those nuts.
After I removed all the nuts the water outlet didn’t want to come off the engine. I used a rubber mallet to do some persuading and it popped off.
I pulled the water outlet off the head. Visible on the underside is the mounting bolt for the generator arm.
Here’s a shot of the inside of the head under the outlet. Surprise! No thermostat. That’s interesting. What looks like a shiny pin in there I believe is a drainage plug that can be removed to drain the engine block.
And here is the water outlet after I gave it a good cleaning with a wire brush, scouring pads, and some Simple Green. It appears it originally was painted Datsun engine blue.